<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <script>

        var str = 'itbaizhan';
        console.log(str.length);
        console.log(str.charAt(4))
        console.log(str.charAt(str.length-1))


    </script>
</body>

</html>